The present invention generally relates to an imaging method for monitoring a body under examination, as well as the apparatus for performing such method.
Currently used monitoring imaging methods are based on the use of apparatuses acquiring high resolution images, mainly volumetric images, in order to have a better and more detailed picture of the body under examination.
Such apparatuses, such as for example CAT, MRI, Fluorangiography, besides generally having a large size and consequently causing drawbacks related to the fact of being cumbersome and to unnecessary costs, they provide a great amount of image data, whose processing is time-consuming and makes impossible to perform imaging sessions in real-time. This drawback is particularly serious when imaging has not only diagnostic purposes but when its further aim is the auxiliary monitoring during operations on the patient.
The need of real-time imaging for assisting operations further increases when the anatomical district or the organ to be monitored change over time or move, such as for example the heart.
In particular the percutaneous introduction of metallic objects either for diagnostic, surgery or therapeutic aims into specific positions of an anatomical district has several drawbacks which need to be solved. The most relevant one resides in the fact that these objects are at least partly made by metal and influence the magnetic field of a standard type tracking system reducing the visibility and the chances for the operation to be successful.
One particular and important example relates to the positioning of cardiac valves. In this case the fact of monitoring the orientation of the valve while introducing it, is very critical for the success of the operation, since a wrong orientation can compromise the operation, making it necessary to replace the valve consequently increasing costs. Cardiac valves generally comprise metal material that affect, while moving the valves, the magnetic field used by standard tracking systems reducing the visibility and the chances for the operation to be successful.
The ideal imaging technique for selecting the type of valve and its relative positioning is Multislice CT due to its high spatial resolution. However, currently such technique, can be used only when planning the operation, for example in order to define the size of the valve, since it cannot be performed in real-time nor in a hemodynamic and/or heart surgery room (so called cathlab) during the operation.
Document EP 1 467 317 discloses a method and an apparatus for combining first and second image data of an object, according to which an ultrasound detector repeatedly generates the first image data of the object and the second image data of the object are generated separately by means of a CT an MR a PET or an x-ray apparatus. The second image data being three-dimensional image data of the object. A combination device combines the first and second image data. A tracker of the ultrasound probe being provided for tracking the position of the ultrasound probe and of the two dimensional data generated by the ultrasound probe. The tracking device is used as a reference coordinate system in relation to which first and second image data can be registered in order to register first and second image data for combination. A certain position of the ultrasound probe and thus of the slice or section plane along which the image data is collected can be thus related to an identical section plane or slice in the three-dimensional image data allowing reconstruction of the image along the slice or section plane by using the second image data instead of the first image data generated by the ultrasound probe.
This device and method uses standard tracking devices in which the position sensors of the ultrasound probe operate in a magnetic field. No arrangement is taken for avoiding magnetic field disturbance in case that the system is used in combination with operations for positioning at least partly metallic objects in the imaged anatomical district.